(a) Field of the Invention
This invention relates to a novel therapeutic use of 1,8-diethyl-1,3,4,9-tetrahydropyrano[3,4-b]indole-1-acetic acid whose generic name is etodolac. More specifically this invention relates to a method for lowering rheumatoid factor blood levels in humans for treatment of rheumatoid arthritis.
(b) Prior Art
The active agent of this invention, 1,8-diethyl-1,3,4,9-tetrahydropyrano[3,4-b]indole-1-acetic acid or a therapeutically acceptable salt thereof, is disclosed in U.S. Pat. No. 3,939,178 issued Feb. 17, 1976. This active agent, hereinafter designated by its generic name etodolac, previously has been reported to be useful as an analgesic and anti-inflammatory agent. (See U.S. Pat. No. 3,939,178).
Rheumatoid factors of the IgM, IgA and IgG classes have been detected in the circulation and are produced locally by the synovium of patients with adult onset rheumatoid arthritis. James S. Goodwin et al in an article entitled "Administration of Nonsteroidal Anti-inflammatory Agents in Patients With Rheumatoid Arthritis" in JAMA, Vol. 250, No. 16, pages 2485-2488 (1983) describes a study wherein pirioxicam was substituted, after two weeks of placebo therapy, in 20 patients who had previously been taking various nonsteroidal anti-inflammatory drugs. The serum rheumatoid factor levels rose when placebo was substituted for the previous drug and piroxicam administration was associated with a fall in rheumatoid factor levels to approximately 62% of the baseline level. I have now found unexpectedly that etodolac, either in its free acid form or in its therapeutically acceptable salt form, is useful for lowering rheumatoid factor blood levels in humans, and particularly humans suffering from arthritis.
This finding, coupled with the fact that etodolac is a relatively safe drug, renders the method of this invention particularly useful and advantageous.